This invention relates to articulated mechanisms and, in particular, to articulated mechanisms employing joints which can be locked or unlocked to move to a selected position. Various mechanisms have been devised to hold tools or workpieces in a desired position. For example, gooseneck mechanisms have been used for lamps as well as articulated arms. However such devices are not always suitable for tasks where it is desired to hold an object selectively in a fixed position without movement or alternatively to easily allow movement of the object when desired.
Earlier patents show lockable ball joints used on articulating apparatuses of various types. For example U.S. Pat. No. 4,616,632 to Wigoda discloses surgical retractors which include ball joints. Foot controllers allow locking of the joints. One version of the invention employs solenoids.
U.S. Pat. No. 5,857,492 to Salamun discloses an electromagnetic friction lock between a spherical joint and its seat.
U.S. Pat. No. 4,527,925 to Bauer et al. discloses a ball joint having a locking element including a spring.
U.S. Pat. No. 4,606,522 to Heifetz shows a jointed holder for holding articles. It includes ball joints which may be tightened.
U.S. Pat. No. 3,638,973 to Poletti discloses a ball joint where pressurized fluid is utilized to make the joint rigid. One application is a surgical retractor.
U.S. Pat. No. 4,767,231 to Wallis discloses an adjustable arm having ball joints. The joints can be locked by applying a compressive force to a push rod.
Russian Patent SU 611039 describes a lockable ball and socket joint using an electromagnet and a spring-like device.
Despite these prior art devices, however, there is a need for a simple, effective, but easy to use articulated mechanism which employs lockable joints.
There is provided, according to one embodiment of the invention, a joint for an articulated mechanism. The joint includes a housing and a rotatable member adjacent to the housing. A friction member is mounted on the housing between the housing and the rotatable member. There is a biasing member normally biasing the friction member against the rotatable member to inhibit rotation of the rotatable member. There is an actuator within the housing operatively coupled to the housing which moves the friction member away from the rotatable member when actuated to facilitate rotation of the rotatable member.
There is provided, according to another embodiment of the invention, an articulated apparatus which includes a plurality of shafts and articulated joints between the shafts. Each joint includes a housing, a rotatable member adjacent to the housing and a friction member mounted on the housing between the housing and the rotatable member. A biasing member normally biases the friction member against the rotatable member to inhibit rotation of the rotatable member. There is an actuator within the housing operatively coupled to the housing which moves the friction member away from the rotatable member when actuated to facilitate rotation of the rotatable member.
For example, at least one articulated joint includes a spherical member connected to the shaft. The housing preferably has a first end, a second end and a hollow interior with a semi-spherical recess at the first end. The spherical member is within the housing member adjacent to the semi-spherical recess. The friction member is between the spherical member and the semi-spherical recess. A ferromagnetic member is within the housing on a side of the spherical member opposite the semi-spherical recess and adjacent to the spherical member. The biasing member is a spring biased between the second end of the housing and the ferromagnetic member to bias the ferromagnetic member against the spherical member and thereby bias the spherical member against the semi-spherical recess to resist movement of the spherical member and the shaft. The actuator is preferably a solenoid mounted on the housing within the hollow interior between the second end of the housing and the ferromagnetic member to attract the ferromagnetic member when actuated to free the spherical member and the shaft for movement.